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Re: [Xen-devel] [PATCH 2/4] x86/hypervisor: pass flags to hypervisor_flush_tlb

> -----Original Message-----
> From: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> Sent: 12 February 2020 18:01
> To: Wei Liu <wl@xxxxxxx>
> Cc: Xen Development List <xen-devel@xxxxxxxxxxxxxxxxxxxx>; Durrant, Paul
> <pdurrant@xxxxxxxxxxxx>; Michael Kelley <mikelley@xxxxxxxxxxxxx>; Wei Liu
> <liuwe@xxxxxxxxxxxxx>; Jan Beulich <jbeulich@xxxxxxxx>; Andrew Cooper
> <andrew.cooper3@xxxxxxxxxx>
> Subject: Re: [PATCH 2/4] x86/hypervisor: pass flags to
> hypervisor_flush_tlb
> On Wed, Feb 12, 2020 at 04:09:16PM +0000, Wei Liu wrote:
> > Hyper-V's L0 assisted flush has fine-grained control over what gets
> > flushed. We need all the flags available to make the best decisions
> > possible.
> >
> > No functional change because Xen's implementation doesn't care about
> > what is passed to it.
> While it's certainly fine to pass a flags field with more information,
> the flush flags for Xen can also contain FLUSH_CACHE, FLUSH_VCPU_STATE
> or FLUSH_ROOT_PGTBL, can you add an assert that those never get passed
> to the flush hook?
> IMO we should define a mask with FLUSH_TLB, FLUSH_TLB_GLOBAL,
> FLUSH_VA_VALID and FLUSH_ORDER_MASK and assert that those are the only
> valid flags to be used for the hypervisor assisted flush hook.

Agreed that this should be abstracted; we certainly don't want to have various 
bits of Xen needing to know what hypervisor it is running on top of.


> Thanks, Roger.
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